a) Field of the Invention
The present invention relates to a multi-purpose adjustable quick expandable installment, and more particularly to an adjustable expandable installment which can be formed integrally, and can save production cost and manual operation fees, thereby constituting a multi-purpose quick and free ascending and descending or expandable installment.
b) Description of the Prior Art
Ordinarily, expansion between two expandable objects, such as between two slabs, between two cylindrical objects, within an expandable foot stand, within an expandable table leg or within a foldable bicycle, is carried out by external screws, springs, snaps, collars or additional outer sleeves, so as to change height or length between the two objects or to fix the two objects to prevent from sliding.
In addition, an existing manhole cover used on a pavement is covered on a through-hole. As it is unable to adjust height of the manhole cover, when the pavement is re-patched, due to that the pavement should be re-paved with asphalt, the patched pavement will have a difference in height as compared to the original pavement that the patched pavement may be higher or lower than the original pavement.
At this time, as it is unable to adjust the height of the ordinary manhole cover, it will also result in the difference in height between the manhole cover and the re-paved pavement after patching the pavement, causing the pavement to be rough that the pavement may be raised or be provided with pots. This will easily endanger road users; especially that it is a rather severe safety risk to the road users who ride on motorcycles or bicycles.
Accordingly, in order to improve the aforementioned issues, there are manhole covers with adjustable height on market. However, as the conventional manhole structures are very complicated, they are inconvenient in production and are not easily operated. Moreover, their functions are limited in that they cannot perform quick fine-adjustment to the height, and they are also more expensive in cost.